Method of casting



INVENTOR. I W M m ATTORNEYS H. u. MCCLELLAND METHOD OF CASTING Filed May 1964 Dec. 1968 Illlll United States Patent 3,417,462 METHOD OF CASTING Howard U. McClelland, Vassar, Mich., assignor to Eaton Yale & Towne Inc., a corporation of Ohio Filed May 5, 1964, Ser. No. 365,069 9 Claims. (Cl. 29526.2)

This invention relates to casting, and more particularly to a method of casting objects having curved or planar surfaces, from gray iron in permanent molds. This invention will be described with reference to a valve plate casting, it being understood that other articles may be formed utilizing the same principles.

The problem has been to find means either mechanical or procedural to eliminate or substantially reduce certain defects, commonly called gas laps, shrinks, rounded corners, voids, etc. which are common in varying degrees in casting relatively smooth, uniform surfaced objects having flat or curved surfaces, and particularly in casting valve plates.

It has been felt that some physical characteristic of the metal has caused these defects. One characteristic, common to all liquids, is surface tension. Little is known about surface tension in gray irons, what causes an excessive amount, or how to reduce or control it metallurgically. Metal entering and filling a cavity in a permanent mold may be considered as a volume of liquid encased in a flexible bag similar to a toy rubber balloon. If this balloon is not broken, air may become trapped and not allowed to escape with the result that gas laps and voids are formed, corners are rounded, and an unsaleable casting is produced. To accomplish this balloon breaking a plurality of horizontal V-shaped serrations are cut in the surfaces of each mold cavity. These serrations are preferably cut .030 deep with corners as sharp as possible. It is not known whether the surface skin is broken by a tearing action of the corners of the serrations, or whether it is the abrupt change in flow direction as the cavity fills that gives the desired results. In any event, the problematic defects have been greatly reduced and substantially eliminated.

This is especially true in the field of casting valve plates having parallel planar surfaces. A considerable improvement has been made in the number of satisfactory valve plates in comparison with those scrapped when the above method is used. It also appears that less blowing, brushing and cleaning of the molds is necessary, which reduces the amount of salvage fiash grinding, and which has practically eliminated warpage, a condition that has always been a problem especially where the slenderness ratio (thickness of width) was low. It is necessary that the ridges formed by the serrations in the cavities be removed by parallel face grinding, but since this operation has previously been performed, no extra work or cost is entailed.

Prior to using the present invention in casting valve plates, the percentage of waste varied between 24-26 percent. Upon using this method of casting the percentage of waste was reduced to a third of the waste previously experienced.

To the accomplishment of the foregoing and related ends, said invention, then, consists of the means hereinafter fully described and particularly pointed out in the appended claims, the following description and annexed drawings setting forth in detail certain illustrative embodiments of the invention, such disclosed means constituting, however, but a few of the various forms in which the principle of this invention may be employed.

In the annexed drawings:

FIG. 1 is a side view of a valve plate produced in a permanent mold cavity without serrations, howing certain defects, such as voids, laps and rounded corners.

FIG. 2 is a cross-sectional view of the valve plate taken in the plane indicated by the line 22 of FIG. 1.

FIG. 3 is a side view of a valve plate casting using this method of casting where serrations are provided in the permanent molds, producing complementary ridges on the casting.

FIG. 4 is a cross-sectional view of the valve plate casting taken in the plane indicated by the line 4-4 of FIG. 2.

Briefly stated this invention is in a method of casting in a permanent mold, a relatively smooth, uniform surfaced member having curved, planar or a pair of substantially parallel curved or planar surfaces, whereby certain defects such as voids, laps and rounded corners are eliminated or substantially reduced. To produce such a casting, indented serrations are provided in the mold. The material is poured into the mold and complementary ridges are formed on the surface or surfaces of the casting. The ridges are then ground away leaving a relatively smooth uniform surface.

Referring more particularly to FIGS. 1 and 2 of the annexed drawings, there is shown a valve plate generally indicated at 2, having parallel planar faces or surfaces 3 and 4, that was cast in a permanent mold not provided with serrations. Also shown in FIGS. 1 and 2 are common defects such as voids and laps which occur in the valve plate surfaces when valve plates arecast in such a manner; for example, the voids indicated at 5 and 6. When these voids occur they are often filled with material forming laps; for example, the lap indicated at 7. However, over a period of time the material used to fill these voids may spall away from the casting or crumple, leaving the original voids.

FIGS. 3 and 4 show a similar valve plate 8, having parallel planar surfaces 9 and 10, cast in a permanent mold provided with a plurality of serrations in accordance with this invention. When poured, these serrations in the mold cause a plurality of corresponding ridges to be formed on the surfaces of the valve plate 8; for example, the ridges 11, 12 and 13 and ridges 14, 15 and 16 formed on the surfaces 9 and 10, respectively, of the valve plate 8 adjacent valve plate edge 17.

The defects such as voids, for example, void 23 are concentrated in the ridges as seen in FIGS. 3 and 4. These ridges are then ground away leaving a smooth uniform surface. The method of grinding commonly used is parallel face grinding in which both faces are simultaneously ground. To insure even or uniform grinding of both faces, a plurality of similar indented serrations are provided in the permanent molds adjacent the opposing edge to produce balancing ridges on the surfaces; for example, ridges 18 and 19, and ridges 20 and 21 formed on surfaces 9 and 10, respectively, adjacent valve plate edge 22. Preferably but not necessarily, the serrations are provided in the mold in a manner such that the ridges formed are substantially parallel and coextensive with the valve plate as shown in FIGS. 3 and 4.

The ridges cast on the surfaces are relatively small. Therefore, where comparatively smooth surfaced castings are acceptable, the grinding operation may be omitted. Only valve plates having substantially parallel planar surfaces are described in reference to the annexed drawings. However, it should be understood that this method of casting is applicable to objects having substantially parallel curved surfaces. This method of casting is also applicable to casting objects having planar or curved surfaces. This improved method of casting is particularly applicable in casting comparatively smooth uniform surfaced objects wherein certain defects commonly called gas laps, shrinks, rounded corners, voids, etc. which are common in varying degrees in castings, especially in valve plate castings are reduced or substantially eliminated.

Other modes of applying the principle of this invention may be employed instead of those specifically set forth above, changes being made as regards the details herein disclosed, provided the elements set forth in any of the following claims, or the equivalent of such be employed.

It is, therefore, particularly pointed out and distinctly claimed as the invention:

1. In a method of casting in a permanent mold, relatively smooth, uniform surfaced ferrous metal objects having a pair of substantially parallel surfaces, wherein gas forming pockets cause defects, the improvement which substantially eliminates said defects comprising:

(a) providing indented serrations in each face of the mold in which said objects are cast,

(b) pouring the metal into said mold causing corresponding ridges wherein said defects are concentrated, to be formed on each of said surfaces, and

(c) removing said ridges containing said defects from surfaces of said object.

2. A method of casting in accordance with claim 1, wherein a plurality of substantially parallel ridge forming serrations are provided in each surface mold.

3. A method of casting in accordance with claim 2, wherein each of said ridge forming serrations is substantially coextensive with the mold.

4. In a method of casting in a permanent mold, a relatively smooth, uniform surfaced ferrous metal object having a planar surface, wherein gas forming pockets cause defects, the improvement which substantially eliminates said defects comprising:

(a) providing indented serrations in the planar face of the mold in which said object is cast,

(b) pouring the metal into said mold causing corresponding ridges wherein said defects are concentrated, to be formed on said planar surface, and

(c) removing said ridges containing said defects from said planar surface of said object.

5. A method of casting in accordance with claim 4, wherein a plurality of ridge forming serrations, substantially parallel and coextensive with said mold, are provided in the planar face of said mold.

6. In a method of casting in a permanent mold, a relatively smooth, uniform surfaced ferrous metal object having a curved surface, wherein gas forming pockets cause defects in said surface, the improvement which substantially eliminates such defects comprising:

(a) providing indented serrations in the curved face of the mold in which said object is cast,

(b) pouring the metal into said mold causing corresponding ridges wherein said defects are concentrated, to be formed on said curved surface, and

(c) removing said ridges containing said defects from said curved surface of said object.

7. A method of casting in accordance with claim 6, wherein a plurality of ridge forming serrations, substantially parallel and coextensive with said mold, are provided in the curved face of said mold.

8. A method of casting valve plates of ferrous metal such that defects normally formed in parallel planar surfaces of said plates, are substantially eliminated; comprising the steps of:

(a) deliberately causing a plurality of parallel, defect concentrating ridges to be formed in planar surfaces of a valve plate during casting; and

(b) removing said ridges after said valve plate casting has solidified.

9. The casting method of claim 8, which includes forming the ridges such that they are substantially co-extensive with said planar surfaces.

References Cited UNITED STATES PATENTS 381,505 4/1888 Munton 29-526.4 1,317,333 9/1919 Sturges 22-183 2,518,055 8/1950 Olsen et al 22183 X 2,923,040 2/1960 Goodwin et al. 22210 X 3,238,578 3/1966 Reinemann 22-183 X 3,242,538 3/1966 Deppeler et a]. 22-204 JOHN F. CAMPBELL, Primary Examiner.

PAUL M. COHEN, Assistant Examiner.

U.S. Cl. X.R. 29526.4, 529 

1. IN A METHOD OF CASTING IN A PERMANENT MOLD, RELATIVELY SMOOTH, UNIFORM SURFACED FERROUS METAL OBJECTS HAVING A PAIR OF SUBSTANTIALLY PARALLEL SURFACES, WHEREIN GAS FORMING POCKETS CAUSE DEFECTS, THE IMPROVEMENT WHICH SUBSTANTIALLY ELIMINATES SAID DEFECTS COMPRISING: (A) PROVIDING INDENTED SERRATIONS IN EACH FACE OF THE MOLD IN WHICH SAID OBJECTS ARE CAST, (B) POURING THE METAL INTO SAID MOLD CAUSING CORRESPONDING RIDGES WHEREIN SAID DEFECTS ARE CONCENTRATED, TO BE FORMED ON EACH OF SAID SURFACES, AND (C) REMOVING SAID RIDGES CONTAINING SAID DEFECTS FROM SURFACES OF SAID OBJECT. 